We report two cases of patients with necrotising myositis who presented initially with limb pain and swelling on a background of respiratory complaints. Patient 1, a previously well 38-year-old female, underwent various investigations in the emergency department for excessive lower limb pain and a skin rash. Patient 2, a 61-year-old female with a background of rheumatoid arthritis and hypertension, presented to accident and emergency feeling generally unwell and was treated for presumed respiratory sepsis. Both deteriorated rapidly and were referred to the plastic surgery team with soft tissue necrosis, impending multiorgan failure and toxaemia. Large areas of necrotic muscle and skin were debrided, which grew group A streptococci,
Group A streptococcus (GAS),
Patient 1 was a previously healthy 38-year-old female with an unremarkable past medical history. She was an immunocompetent nonsmoker with a normal body mass index. She presented to her general practitioner (GP) with acute left lower leg pain and swelling. Three weeks prior to this she had a progressive productive cough, swinging fever, and malaise. Her GP suspected a deep venous thrombosis (DVT) and concurrent chest infection and prescribed oral antibiotics. She was referred the same day to a DVT clinic in another institution. No DVT was identified on ultrasound with venous duplex scan but muscle swelling with no sonographically identifiable cause was noted. The DVT team were concerned about the patient and asked for a medical opinion. She was subsequently admitted under the medics.
Over the next few hours the patient started to deteriorate and her leg pain and swelling worsened. Only venous duplex was available in the DVT clinic and so the team could not rule out acute limb ischaemia. Once the team had identified diminished distal arterial pulses she was urgently referred and transferred to the vascular surgeons at our regional centre to investigate the possibility of an acute vascular event. However, she arrived haemodynamically unstable. She also complained of mild back pain, so a thromboembolic event associated with an acute aortic dissection was suspected. As dissection was queried, an urgent aortic computed tomography angiogram (CTA) was arranged, which did not identify any evidence of vascular disease. However, a cavity was noted in the lower lobe of her right lung, which was reported as a likely lung abscess (Figure
CT scan with contrast showing a right lung abscess, the most likely seeding source for patient 1’s invasive muscle infection.
Patient 2 was a 61-year-old lady with a past history of poorly controlled rheumatoid arthritis and hypertension, but independent in all activities of daily living. She presented to the emergency department with acute pain in both her lower limbs and right arm. Preceding this, she had experienced generalised myalgia, anorexia, vomiting, and flu-like symptoms for 3 days. She had also received an intramuscular steroid injection into her right buttock 5 days earlier for a flare-up of rheumatoid disease. As part of her rheumatoid treatment she also took regular hydroxychloroquine, leflunomide (pyrimidine synthesis inhibitor), and weekly methotrexate alongside the steroid injections for flare-ups and would have been immunosuppressed as a result. On admission she was septic, in fast atrial fibrillation with a heart rate of 150 beats per minute, but maintaining a blood pressure of 130/80 mmHg. Her examination revealed bibasal lung crepitations and a tender, but soft right calf. There was no evidence of pyomyositis at her injection site on her right buttock. She was commenced on digoxin, antibiotics for presumed chest sepsis, and fluid resuscitation. She deteriorated, becoming hypoxic and haemodynamically unstable, and was admitted to the intensive care unit (ICU).
Patient 1 continued to deteriorate clinically with pyrexia, resistant shock, and toxaemia. Arterial blood samples showed acute lactic acidosis with a PH of 7.2 and lactate of 7.9 mmol/L. Her biochemical profile showed acute kidney injury (AKI) with raised creatinine kinase (CK) and acute liver injury as demonstrated in Table
Blood results from patients 1 and 2 taken upon admission to our hospital before plastic surgery referral.
Test | Patient 1 | Patient 2 | Units | Range |
---|---|---|---|---|
Haemoglobin | 15.3 | 12.0 | g/dL | 12–15 |
Sodium | 127 | 125 | mmol/L | 135–145 |
Potassium | 5.1 | 3.7 | mmol/L | 3.5–5.0 |
Urea | 10.1 | 15.1 | mmol/L | 2.5–6.7 |
eGFR | 34 | 19 | mL/min/1.73 m2 | |
Creatinine | 150 | 222 | umol/L | 54–145 |
Bilirubin | 62 | 7 | umol/L | 3–17 |
ALT | 249 | 52 | IU/L | 10–45 |
AST | 817 | — | IU/L | 15–42 |
ALP | 450 | 146 | IU/L | 75–250 |
Albumin | 31 | 26 | g/L | 35–50 |
Creatine kinase | 35040 | 1948 | IU/L | 24–195 |
Glucose | 5.2 | 6.5 | mmol/L | |
INR | 1.8 | 1.5 | ratio | 0.7–1.2 |
WCC | 6.93 | 29.8 | ×109/L | 4.0–11.0 |
CRP | >156 | >156 | mg/L | 0–8 |
eGFR: estimated glomerular filtration rate (automated); ALT: alanine aminotransferase; AST: aspartate aminotransferase; ALP: alkaline phosphatase; INR: international normalised ratio; WCC: white cells count; CRP: C-reactive protein.
Patient 2 also deteriorated, becoming tachycardic, hypotensive, and hypoxic. Bedside echocardiography showed no evidence of ventricular dysfunction and a collapsed inferior vena cave (IVC). A chest radiograph confirmed right lower zone consolidation, which was presumed to be from an infective process and hence diagnosed as pneumonia (Figure
Chest radiograph taken of patient 2 showing right lower lobe consolidation consistent with pneumonia.
Patient 1 was urgently referred to the plastic surgical team with suspected necrotising fasciitis. Rhabdomyolysis was considered as a diagnosis given her vastly elevated creatine kinase; however once the skin changes were detected alongside the pyrexia and signs of shock a necrotising condition became the lead diagnosis. Following plastics assessment, including incision of the skin to deep fascia under local anaesthetic and visualisation of necrotic tissue, the patient was resuscitated and started on broad spectrum intravenous antibiotics (meropenem, vancomycin, and clindamycin due to penicillin allergy). She was taken to theatre for emergency surgical exploration and debridement. Almost the entire posterior compartment of the left lower leg was necrotic and hence an extensive excision of the dead tissues was performed (Figure
This figure shows patient 1’s extensive debridement of the left lower leg following identification of necrotic tissue. This theatre picture at the second look also shows the skin changes developing on the right leg, a late clinical sign.
Patient 2 was treated initially as sepsis, likely secondary to pneumonia in an immunocompromised patient (from her disease modifying antirheumatic drugs and recent steroid injection). She was treated with intravenous co-amoxiclav and clarithromycin and fluid resuscitation and admitted to ICU. After admission her right calf became increasingly swollen, firm, and tender. Erythema on her torso was noted. Her oxygen and inotropic requirements increased and her repeat bloods showed increased CK of 7206 and worsening coagulopathy. She was intubated within 24 hours of being on ICU. A vascular opinion was sought for possible compartment syndrome of her lower limbs. All pulses were present and compartment syndrome was considered unlikely. A computed tomography (CT) of chest, abdomen, and pelvis alongside an ultrasound of the right calf was arranged and antibiotics changed to clindamycin and Tazocin (piperacillin and tazobactam). The CT showed soft tissue swelling in the upper right buttock of unknown significance. Ultrasound of the right lower limb showed oedema and swollen muscles. Blistering around the right groin and right arm was noted at 30 hours after admission. The plastic surgery team reviewed this urgently. Incision of skin to deep fascia under local anaesthetic on ICU showed necrotic soft tissue. Suspecting necrotising fasciitis or myositis, an emergency surgical exploration was arranged. The majority of the medial head of gastrocnemius and half of soleus muscle of her right leg were found to be necrotic. Similar necrotic changes were found within her right biceps muscle with inflamed fascia. Extensive debridement was performed and multiple samples were sent for microbiological analysis. Intraoperative samples yielded GAS (
Patient 1 recovered from her toxaemia and overwhelming sepsis but had large bare areas of exposed muscles and fascia. She was transferred to a nearby burns unit for major skin reconstruction and rehabilitation. She had staged skin allografting with satisfactory results. She is currently awaiting a left leg prosthesis before she undergoes an intensive rehabilitation programme. She would be followed up by cardiothoracic surgeons with a repeat lung CT scan to assess her lung abscess.
Patient 2, in contrast, deteriorated in ICU postoperatively. Her AKI worsened, requiring continuous venovenous hemodiafiltration. Her inotropic requirements increased and metabolic acidosis worsened. Repeat echocardiography showed worsening left ventricular function with an ejection fraction of 10–20%. After discussion with her relatives a decision was made to withdraw inotropes and palliate her. She died just over 48 hours after admission.
Necrotising myositis is a severe but rare form of acute invasive GAS infection with high rates of morbidity and mortality. Overwhelming invasive GAS muscle infections are rare with no more than 30 cases reported over the last century [
Streptococcal necrotising myositis (SNM) generally affects healthy, middle-aged patients with the involvement of a single muscle group. This usually represents the thigh, calf, or arm muscle groups [
Diagnosis of SNM is challenging because of its rarity and diverse clinical presentation at early, intermediate, and late stages [
Severe SNM can cause marked systemic toxic effects, namely, the streptococcal toxic shock syndrome (STSS), as defined by the Working Group on Severe Streptococcal Infections criteria [
Differentiating SNM from NF clinically can be challenging as the skin manifestations are similar [
The LRINEC is another tool that can be used in the diagnostic conundrum presented by necrotising infections. Focussing on biochemical abnormalities, anaemia, leukophilia, raised CRP, hyponatraemia, raised creatinine, and hyperglycaemia, the LRINEC can aid differentiation of necrotising soft tissue infections from other soft tissue infections (Table
LRINEC scoring for patient 1 and patient 2. The table is modified from Wong et al., 2004 [
Parameter | Range | Score | Patient 1 | Patient 2 |
---|---|---|---|---|
CRP (mg/L) | <150 | 0 | ||
>150 | 4 | 4 | 4 | |
|
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WBC (cells/mm3) | <15 | 0 | 0 | |
15–25 | 1 | |||
>25 | 2 | 2 | ||
|
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HB (g d/L) | >13.5 | 0 | 0 | |
11–13.5 | 1 | 1 | ||
<13.5 | 2 | |||
|
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Creatinine | <141 | 0 | ||
>141 | 2 | 2 | 2 | |
|
||||
Sodium (mmol/L) | >135 | 0 | ||
<135 | 2 | 2 | 2 | |
|
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Glucose (mmol/L) | <10 | 0 | 0 | 0 |
>10 | 1 | |||
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Total |
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|
In cases of diagnostic uncertainty, we advocate incision biopsy under local anaesthetic, through fascia for suspected SNM, with samples sent for urgent microscopy and histology [
With comparable pathology and management, outcome was vastly different between these two cases. It should be recognised that premorbid state and physical fitness influence outcome as suggested by our cases.
In SNM soft tissue changes are subtle and occur late compared with NF. A high index of suspicion for SMN in all cases presenting with acute disproportionate limb pain associated with systemic deterioration. Early and aggressive antibiotic therapy with a combination of penicillin and clindamycin is imperative for suspected cases of SMN. Early referral to a surgical team for aggressive excision and debridement of infected tissues is crucial and early amputation should be considered if indicated.
For details see Figures
The authors declare that there is no conflict of interests regarding the publication of this paper.